Nuxeo Enterprise Platform: User Notification Service Core.
This service handle user notification when events occur in the platform.
Notifications are configurable (through extension points) and can be sent
via several channels (currently only email is supported but IM support is
planned).

Nuxeo Enterprise Platform: The Placeful Configuration Service
allow component to declare configuration/annotation on content objects.
This is mainly use to define and store configuration of content/service
(ex: subscription to user notifications on a given folder). This service
also manage configuration inheritance in the content tree (ex: on this
particular folder, get all "subscriptions" from users to this
notification with inheritance from parent folders).